Asthma is a common chronic disease resulting in significant morbidity and health resource utilisation, and multiple therapeutic options exist. Clinicians and healthcare providers need accurate information on the clinical and cost- effectiveness of asthma treatments to make informed decisions on management strategies. Randomised, controlled trials demonstrate cause and effect relationships between treatments and outcomes, but their tight entry criteria and strict study protocols mean that their results cannot automatically be generalised or used for economic modelling. There is a need for observational data to examine the effectiveness of alternative interventions in routine practice. Clinical and administrative databases are a possible information source for observational studies, and are increasingly used in asthma clinical, epidemiological and economic research. This paper examines the types of database used, the advantages and limitations of such studies and considers quality markers. High quality database studies can provide important epidemiological and economic information that can be of value in understanding the causes and effective management of asthma.